Low-cost porous carbon core-shell nanosphere as well as preparation and application thereof

Abstract

The invention relates to a low-cost porous carbon core-shell nanosphere as well as preparation and application thereof. The preparation method comprises the following steps: dissolving a base catalyst, a carbon precursor and a silicon dioxide precursor in an organic solvent / water mixed solution; carrying out hydrolytic polymerization on the carbon precursor and the silicon dioxide precursor under the action of alkali catalysis, and carrying out phase separation and precipitation to form silicon dioxide-polymer core-shell nanospheres; then performing high-temperature carbonization to form silicon dioxide and carbon core-shell nanospheres; and further performing etching treatment to obtain the porous carbon nanospheres. The size of the prepared porous carbon core-shell nanosphere is 100-2000 nm, the specific surface area of the porous carbon core-shell nanosphere is 500-2000 m < 2 > / g, and the carbon content of the porous carbon core-shell nanosphere is 95-99 wt%. The raw materials are easy to obtain, the method is simple, and the cost is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon materials, and relates to a low-cost porous carbon core-shell nanosphere and its preparation and application. Background Art

[0002] As an emerging non-silicon-based porous material in the field of porous carbon materials, its excellent electrical conductivity, good mechanical stability and thermal stability play an increasingly important role in catalysis, adsorption, separation, hydrogen storage, electrochemistry and other aspects. Among them, the spherical morphology of porous carbon is particularly prominent among various porous carbon morphologies, because while having the inherent advantages of porous materials, it also has the highest tapped density and loading capacity, and has excellent commercial potential. However, the actual application of porous carbon spheres is still in its infancy. One of the restrictive factors is that the large-scale production of porous carbon core-shell nanospheres has not been realized and is still in the laboratory synthesis stage, which is difficult to meet the increasing demand for porous carbon in many fields. Therefore, the realization of the large-scale production of porous carbon core-shell nanospheres will greatly promote the process of the practical application of this material, and has very important theoretical and practical significance.

[0003] Another important influencing factor is the cost required for preparation. Most of the methods used in the laboratory are hard template methods. This method has cumbersome steps and requires the sacrifice of hard templates, resulting in high costs. The currently most commonly used soft template methods include direct precipitation, quasi-liquid crystal template and solvent evaporation-induced self-assembly. It not only avoids the cost problem caused by the loss of hard templates, but also simplifies the preparation process. At present, some porous carbon materials have been industrialized, but due to production and process limitations, these materials still have high prices and poor consistency. Developing porous carbon materials with good consistency and high yield is still a challenge.

[0004] For example, Chinese Patent CN202110870376.8 provides a porous silicon@carbon core-shell nanosphere for the negative electrode of a lithium-ion battery and its preparation and application. It dissolves an alkali catalyst, a carbon precursor and a silica precursor in an organic solvent / water mixed solution; the carbon precursor and the silica precursor are hydrolyzed and polymerized under the catalysis of an alkali, and phase separation precipitation forms a silica@polymer core-shell nanosphere; then it is carbonized at high temperature to form a silica@carbon core-shell nanosphere; further, through molten salt reduction, a porous silicon@carbon nanosphere is obtained. However, the molten salt reduction method used in this patent has high energy consumption, and it is difficult to control the reaction conditions and the degree of reaction, resulting in inconsistent sizes of the generated nanospheres and poor consistency in the pore size distribution inside the spheres, which greatly limits its application in the fields of adsorption separation and lithium-ion batteries. In addition, the environmental pollution risk brought by this patent cannot be ignored. Summary of the Invention

[0005] The object of the present invention is to provide a low-cost porous carbon core-shell nanosphere and its preparation and application, which have good size consistency, high carbon content, high yield, simple operation, easy control of reaction conditions, etc.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] In the first aspect, the present invention provides a low-cost porous carbon core-shell nanosphere with a size of 100 - 2000 nm, a specific surface area of 500 - 2000 m 2 / g, and a carbon content of 95 - 99 wt%.

[0008] In the second aspect, the present invention provides a method for preparing a low-cost porous carbon core-shell nanosphere, comprising the following steps:

[0009] S1. Dissolve an alkali catalyst in a mixed solution of an organic solvent / water, then add a carbon precursor and a silica precursor, stir and react, separate, dry, and calcine the obtained precipitate to obtain a silica@carbon core-shell nanosphere;

[0010] S2. Pour the silica@carbon core-shell nanosphere into an NaOH solution for etching, filter and dry to obtain a porous carbon core-shell nanosphere, which is the target product.

[0011] Further, in S1, the alkali catalyst is selected from one or more of organic bases or inorganic bases, wherein the inorganic base is selected from one or more of ammonia water, sodium hydroxide, and potassium hydroxide;

[0012] The organic base is selected from one or more of methylamine, ethylamine, octylamine, dodecylamine, triethanolamine, and diethanolamine. Preferably, the alkali catalyst is ammonia water or sodium hydroxide.

[0013] Further, in S1, in the mixed solution, the volume ratio of the organic solvent to water is (0.4 - 2):1, preferably 0.4:1;

[0014] The organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, cyclohexane, or n-hexane, preferably ethanol, etc.

[0015] Further, in S1, the carbon precursor is composed of a phenolic substance and an aldehyde substance in a molar ratio of 1:(0.8 - 10), wherein the phenolic substance is selected from one or more of phenol, resorcinol, catechol, hydroquinone, o-methylphenol, p-methylphenol, and m-methylphenol;

[0016] The aldehyde substance is selected from one or more of formaldehyde, acetaldehyde, propionaldehyde, or salicylaldehyde.

[0017] Further, in S1, the silica precursor is selected from one or more of sodium silicate, tetraethyl orthosilicate, tetramethyl orthosilicate, fumed silica, trichlorosilane, tetrachlorosilane, sodium metasilicate, silica aluminate, 1,4-bis(triethoxysilyl)benzene, bis(triethoxysilyl)ethylene, methoxydimethylphenylsilane, (diphenylmethyl)trichlorosilane, bis(p-bromophenyl)dimethylsilane, and ethoxytriethylsilane. Preferably, it is tetraethyl orthosilicate or the like.

[0018] Further, in S1, the molar ratio of the base catalyst, carbon precursor, silica precursor to the organic solvent is (0.5 - 20):(1.8 - 11):(1 - 10):(50 - 200).

[0019] Further, in S1, the temperature of the stirring reaction is 25 - 35 °C, and the time is 18 - 30 h, preferably 24 h;

[0020] The calcination is carried out in an inert atmosphere, the calcination temperature is 600 - 800 °C, and the calcination time is 2 - 24 h.

[0021] Further, in S2, the concentration of the NaOH etching solution is 2 - 10 mol / L, and the etching time is 12 - 24 h.

[0022] In a third aspect, the present invention provides an application of a low-cost porous carbon core-shell nanosphere in the preparation of a lithium-ion battery electrode.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The porous carbon nanospheres prepared by the present invention have a carbon content of 95 - 99 wt%, a size of 100 - 2000 nm, and a specific surface area of 500 - 2000 m 2 / g.

[0025] (2) The porous carbon nanospheres have a porous spherical structure and have irreplaceable advantages in the transport properties and tap density of the material.

[0026] (3) The porous carbon material can improve the conductivity of the electrode material and ensure the transmission of electrons. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a preparation flow chart of the porous carbon core-shell nanosphere of the embodiment of the present invention;

[0028] Figure 2 It is a transmission electron microscope image of the porous carbon core-shell nanosphere provided in Example 1 of the present invention;

[0029] Figure 3 It is a scanning electron microscope image of the porous carbon core-shell nanosphere provided in Example 1 of the present invention;

[0030] Figure 4 This is the thermogravimetric curve of the porous carbon core-shell nanospheres provided in Example 1 of the present invention;

[0031] Figure 5 This is the X-ray diffraction pattern of the porous carbon core-shell nanospheres provided in Example 1 of the present invention;

[0032] Figure 6 This is the nitrogen adsorption-desorption isotherm of the porous carbon core-shell nanospheres provided in Example 1 of the present invention;

[0033] Figure 7 This is the pore size distribution diagram of the porous carbon core-shell nanospheres provided in Example 1 of the present invention. Detailed implementation manners

[0034] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0036] The term "and / or", "or / and", "and / or" as used herein includes any one of the two or more related listed items, and also includes any and all combinations of the related listed items. The said any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items. It should be noted that when at least two conjunctions selected from "and / or", "or / and", "and / or" are used to connect at least three items, it should be understood that in this application, this technical solution undoubtedly includes the technical solution connected by "logical AND", and undoubtedly includes the technical solution connected by "logical OR".

[0037] In this application, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0038] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0039] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or upper limit and combined with any other point or single numerical value or with other lower limits or upper limits to form a range not explicitly recited.

[0040] In this application, the temperature parameter, unless otherwise specified, allows both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuation within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C is allowed.

[0041] In this document, the "suitable combination method", "suitable method", "any suitable method", etc., the "suitable" described therein is subject to being able to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0042] In this application, "further", "even further", "especially", etc. are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0043] In this application, "optionally", "optional", "option", mean that it can be either present or absent, that is, it refers to any one of two alternative schemes of "present" or "absent". If "optional" appears multiple times in a technical solution, unless otherwise specified and there are no contradictions or mutual restrictions, each "optional" is independent of each other.

[0044] In the description of the application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0045] Unless otherwise specified, all formulations and tests occur in an environment of 25°C in this document.

[0046] In this text, "include", "comprise", "contain", "have" or other variants are intended to cover non-closed inclusion, and no distinction is made among these terms. The term "comprise" means that other steps and components can be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and consist essentially of the essential elements and limitations described herein, as well as any additional or optional components, ingredients, steps or limitations described herein. No distinction is made among the terms "efficacy", "performance", "effect", and "function" in this text.

[0047] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution. If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0048] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, and preferably sequentially.

[0049] Example 1:

[0050] A method for preparing a porous carbon core-shell nanosphere, see Figure 1 , including the following steps:

[0051] First, 0.5 ml of ammonia water (concentration 28 wt%) was added to a mixed solution of 140 ml of ethanol / water (volume ratio 2:5). After stirring for 30 minutes to mix evenly, 3.6 ml of tetraethyl orthosilicate, 1 g of resorcinol, and 1.4 ml of formaldehyde solution (concentration 37 wt%) were added respectively, and the reaction was carried out at room temperature for 24 h. Then, after centrifugation and washing, the sample was placed in a tube furnace protected by a nitrogen atmosphere and calcined at 800 °C for 4 h to obtain silica@carbon nanospheres. The obtained nanospheres were placed in 2 mol of NaOH solution and stirred overnight, then filtered and dried to obtain a sample with a size of ~280 nm, a carbon content of ~95 wt%, and a specific surface area of 1556 m 2 / g. Under the BJH model fitting of a nitrogen adsorption-desorption tester, the D10 pore diameter of this sample is 1.8 nm, and the D90 is 5.2 nm, with excellent pore size concentration.

[0052] Example 2:

[0053] A method for preparing a porous carbon sphere, including the following steps:

[0054] First, 1 ml of ammonia water was added to a mixed solution of 140 ml of ethanol / water (volume ratio 2:5). After stirring for 30 minutes to mix evenly, 5 ml of tetraethyl orthosilicate, 1 g of resorcinol, and 1.4 ml of formaldehyde solution were added respectively, and the reaction was carried out at room temperature for 24 h. Then, after centrifugation and washing, the sample was placed in a tubular furnace protected by an argon atmosphere and calcined at 800 °C for 4 h to obtain silica@carbon nanospheres. The obtained nanospheres were placed in 2 mol of NaOH solution and stirred overnight, then filtered and dried to obtain a sample with a size of ∼2000 nm, a carbon content of ∼98 wt%, and a specific surface area of 1226 m 2 / g. The D10 pore diameter of this sample is 1.9 nm, and D90 is 5.3 nm, with excellent pore diameter concentration.

[0055] As can be seen from the Figure 2 , 3 the porous carbon core-shell nanospheres produced by the present invention are of uniform size and the pore shape is obvious; Figure 4 It shows that the mass of the carbon spheres at 800 °C is close to 0, Figure 5 and the XRD test also shows no impurity peaks, indicating that the ash content of the sample is extremely low and there are no impurities. Figure 6 , 7 The BET test curve shows extremely high adsorption volume and narrow pore size distribution, indicating good pore diameter consistency inside the carbon spheres and excellent specific surface area.

[0056] Comparative Example 1:

[0057] Compared with Example 1, most of them are the same, except that the silica@carbon nanospheres are treated by the molten salt reduction method in Example 1 of CN202110870376.8. The results show that the sizes of the porous carbon spheres in the comparative example range from ∼200 nm to 20 μm, and the average specific surface area is only 819 m 2 / g. The non-uniformity of the size will make the loading process of the porous carbon spheres more difficult to control. Screening and grading before use not only increase the cost, but also often cause waste of unqualified products, greatly limiting their commercialization. In addition, the D10 pore diameter of this sample is 6.5 nm, and D90 is 113.6 nm, with poor pore size distribution consistency, further proving the advantages of the present invention in producing porous carbon spheres with uniform pore channels and high specific surface area.

[0058] The post-treatment method of etching with alkali solution and other methods used in the present invention retains the original pore shape to the greatest extent, has less damage to the internal structure of the carbon spheres, and greatly improves the specific surface area and pore volume of the material.

[0059] The above description of the embodiments is provided to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A low-cost porous carbon core-shell nanosphere, characterized in that: Its size is 100-2000nm and its specific surface area is 500-2000m 2 / g, and the carbon content is 95-99wt%.

2. The method for preparing a low-cost porous carbon core-shell nanosphere according to claim 1, characterized in that: The following steps are involved: S1, dissolving the base catalyst in a mixed solution of organic solvent / water, then adding a carbon precursor and a silicon dioxide precursor, stirring for reaction, separating, drying, and calcining the obtained precipitate to obtain silicon dioxide@carbon core-shell nanospheres; S2. Pour the silicon dioxide@carbon core-shell nanospheres into a NaOH solution for etching, filter, and dry to obtain porous carbon core-shell nanospheres, which are the target product.

3. The method for preparing a low-cost porous carbon core-shell nanosphere according to claim 2, characterized in that: In S1, the base catalyst is selected from one or more organic bases or inorganic bases, wherein the inorganic base is selected from one or more selected from ammonia water, sodium hydroxide, and potassium hydroxide; The organic base is selected from one or more of methylamine, ethylamine, octylamine, dodecylamine, triethanolamine and diethanolamine.

4. The method for preparing a low-cost porous carbon core-shell nanosphere according to claim 2, characterized in that: In S1, the volume ratio of the organic solvent to water in the mixed solution is (0.4-2):1; The organic solvent is selected from one or more of methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, cyclohexane or n-hexane.

5. The method for preparing a low-cost porous carbon core-shell nanosphere according to claim 2, characterized in that: In S1, the carbon precursor is composed of a phenolic substance and an aldehyde substance in a molar ratio of 1:(0.8-10), wherein the phenolic substance is selected from one or more of phenol, resorcinol, catechol, hydroquinone, o-methylphenol, p-methylphenol, and m-methylphenol; The aldehyde substance is selected from one or more of formaldehyde, acetaldehyde, propionaldehyde or salicylaldehyde.

6. The method for preparing a low-cost porous carbon core-shell nanosphere according to claim 2, characterized in that: In S1, the silicon dioxide precursor is selected from one or more of sodium silicate, ethyl orthosilicate, methyl orthosilicate, fumed silica, trichlorosilane, tetrachlorosilane, sodium metasilicate, oxidized aluminosilicate, 1,4-bis(triethoxysilyl)benzene, bis(triethoxysilyl)ethylene, methoxydimethylphenylsilane, (diphenylmethyl)trichlorosilane, di(p-bromophenyl)dimethylsilane, and ethoxytriethylsilane.

7. The method for preparing a low-cost porous carbon core-shell nanosphere according to claim 2, characterized in that: In S1, the molar ratio of the base catalyst, the carbon precursor, the silicon dioxide precursor and the organic solvent is (0.5-20): (1.8-11): (1-10): (50-200).

8. The method for preparing a low-cost porous carbon core-shell nanosphere according to claim 2, characterized in that: In S1, the stirring reaction temperature is 25-35°C and the time is 18-30h; The calcination is carried out in an inert atmosphere at a temperature of 600-800° C. and a calcination time of 2-24 hours.

9. The method for preparing a low-cost porous carbon core-shell nanosphere according to claim 2, characterized in that: In S2, the concentration of the NaOH solution is 2-10 mol / L, and the etching time is 12-24 h.

10. Use of the low-cost porous carbon core-shell nanospheres according to claim 1 in the preparation of lithium-ion battery electrodes.

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